Spasticity occurs in 20% to 40% of stroke patients. Two new studies add to the body of evidence supporting the use of botulinum toxin type A (BT-A) injections for post-stroke spasticity: the first looked at the ideal timing of injections for plantar flexor spasticity, and the second looked at ultrasound-guided injections for spastic equinovarus.
Chronic plantar flexor spasticity concomitant with equinovarus, a common complication from stroke, leads to reduced foot clearance and circumduction of the involved leg during the gait cycle. Previous randomized controlled trials have shown that BT-A injected into the gastrocnemius muscle increases range of motion in the ankle, preventing spastic equinovarus. Ongoing research supports the use of BT-A injections in the subacute recovery phase of stroke rehabilitation, moving the timing up from prior reports to within the 6-month window post-event. Although the thinking is to prevent the development of abnormal muscle and motor activities, the potential for post-injection weakness at this early stage presents a clinical challenge. But so too does waiting too long to perform the injections, which can allow spasticity to become chronic, leading to secondary issues such as stiffness or fibrosis of surrounding tissues, thus compromising responsiveness to treatment overall.
To address this question, a Korean research team led by Hyun-Mi Oh, who had previously done a randomized controlled trial comparing the efficacy of different BT-A injection sites in the gastrocnemius (GC) for the treatment of spasticity, performed a secondary analysis of that data. This new analysis sought to understand whether the timing of the BT-A injection could affect reduction in plantar flexor spasticity or improve gait, specifically comparing those who received injections within 6 months of the stroke event (n = 12), those who received the injection between 6 and 12 months (n = 14), and those who received the injection between 1 and 2 years post-event (n = 12). Outcome measures included the Modified Ashworth Scale (MAS), ABILICO, Functional Ambulation Category, and others. Data were analyzed for baseline and 2, 4, and 8 weeks post-injection.
All 3 patient groups showed improvement in spasticity and gait post-injection. Per the MAS, significant improvement was seen as early as 2 weeks (P <.001). Gait improvements, based on ABILICO and Functional Ambulation Category assessments, were apparent for all 3 groups at the 8-week measure. The authors concluded that, regardless of the timing, the injection could be expected to lead to improvement in both spasticity and gait, and that the injections were beneficial and safe, even in the early phase of stroke rehabilitation.
The second study, conducted by Semra Aktürk and coworkers, looked at the use of ultrasound to guide injections into the innervation zones of the gastrocnemius (GC), soleus (S), and tibialis posterior (TP). Each of 23 post-stroke patients received injections of BT-A 25 U in the GC medial head, GC lateral head, S, and TP. Assessments made at 4 and 12 weeks post-injection included MAS, Brunnstrom stage, and Preferred Gait Speed.
MAS scores showed all patients had improved muscle tone at both 4 and 12 weeks. Brunnstrom scores showed improvements at 12 weeks post-injection. Gait speed showed continuous improvement from baseline to 4 weeks and through 12 weeks. The authors concluded that the ultrasound guidance, based on the EURO-musculus approach for lower extremity muscles, allowed the injected toxin into the innervation zones of hard-to-reach deep muscles, but avoided the neurovascular injuries that can occur with conventional needle insertion. The authors note, however, that BT-A injections alone do not improve spasticity, but rather that they should be part of a focused rehabilitation program that seeks functional improvements by reducing abnormal sensory inputs and uncontrolled motor activity.
Oh HM, Park GY, Choi YM, et al. The effects of botulinum toxin injections on plantar flexor spasticity in different phases after stroke: a secondary analysis from a double-blind, randomized trial. PM R. 2018 Mar 3. pii: S1934-1482(17)30113-2.
Aktürk, S., Büyükavcı, R., Ersoy, Yü. Functional outcomes following ultrasound-guided botulinum toxin type A injections to reduce spastic equinovarus in adult post-stroke patients. Toxicon. 2018 Mar 9. pii: S0041-0101(18)30113-2.